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On Monday 22 October 2007 13:51, Eric Lavigne wrote:
> > "build your own sputnik" -- not instructions, but a challenge ...
> >
> > http://news.bbc.co.uk/2/hi/uk_news/magazine/7049002.stm
>
> Easy to build, not so easy to launch. 

There is a small satellite design club at UF. If you want a launch 
opportunity, they are probably your best bet. http://www.ufsmallsat.com/

The article was rather misleading. I don't think the reporter did much 
research before writing it.  There have been over 60 amateur satellites in 
space, starting with OSCAR-1 in 1961.

http://www.projectoscar.net/ 
http://www.amsat.org/

The only reason I can think of to build a pressurized satellite is to 
duplicate Sputnik-1.

Antennas are pretty straightforward -- a dipole made from steel tape measure 
folded up so it automatically deploys itself when the satellite releases has 
often been used.

The chance of your satellite being hit by space debris before it dies of some 
other cause is negligible.

> It would be neat if someone could get
> around the legal/political obstacles for allowing homemade launches.
> Probably too difficult in the USA.

If you are talking about building your own launch vehicle, the legal obstacles 
are negligible. Private groups have spent millions of dollars on it and not 
yet succeeded.

If you want to launch on someone else's vehicle, one of the hard parts of 
designing a home-made satellite is meeting the outgassing requirements. No 
modern launch vehicle is going to allow you aboard until  you prove you don't 
outgas anything that might damage other payloads. It seems to be a pretty 
tough requirement, requiring the correct selection of paints, plastics, etc. 
I know you all like America-bashing, but it isn't just an American thing, and 
it isn't a political thing. Many amateur satellites are launched on French 
and Russian boosters, and they have pretty much the same requirements. You 
want a launch opportunity, you have to prove you aren't going to ruin a 
billion dollars worth of other people's stuff. And you have to be willing to 
pay the launch fee. The problem is that the amateurs have been so successful 
at launching useful satellites packed away in the unused corners of a launch 
vehicle, that the commercial people are now using those strategies and there 
are no longer unused corners. 

A large amateur satellite can expect to pay $100K or more for a ride on a test 
flight of a new booster. That's dirt cheap -- I'd guess it covers only the 
actual costs to the launch organization. And you have a good chance of 
blowing up. Typical amateur satellites are now 10 cm cubes and under 1 kg 
mass. This is a standard format and they are launched in groups from a 
standard canister that has already been approved for most major launch 
vehicles. The fee is (or was a few years ago) $50K for your little cube. 
There are opportunities for educational institutions to get this fee covered 
by various programs, hence the UF club.

It used to be possible for educational groups to get rides (and sometimes 
launches) for their payloads on the Space Shuttle at very affordable prices 
(e.g. $2K), but I don't know if it still is.

More info:
http://www.hobbyspace.com/SatBuilding/index.html
http://centaur.sstl.co.uk/SSHP/nano/
http://www.delfic3.nl/index.php?option=com_content&task=view&id=34&Itemid=50
http://cubesat.calpoly.edu/
http://ssdl.stanford.edu/ssdl/images/stories/papers/2002/ssdl0205.pdf (a pdf 
describing a typical experimental satellite design)

- Bob